Method of refining vegetable oils in miscella



Patented Feb. 23, 1954 [METHOD OEREFINING VEGETABLE OILS I IN MISCELLA a .J'ohnJAJZiegler, Toronto, Ontario,- Carrada; as-

f signnr to Ganadian Breweries Limited, Toronto, out-aria, (531136343; corporation ofvOntario No'Drawing. Application September "28.;1950, Serial- No. 187,353

This invention'relatesto: a process for refining vegetable oils in 'misoel-la.

"Vegetable oils are usual-1y extra'cted" from the eourcezrnaterialieither by oold or hot pressing, or by solvent extraction (such as hexane) followed by removal, ithrou'gh"distillation, of' the solvent. each case i aerude' oil results. "Conventional treatmentsof this crude 'oil begins with a degummingstep which ginns; resins, phosphatides, sterols ran-d- :some'wraxes-v are precipitated vfrom .the oilxa-fter agitatin jt with l to '1'0% of water at'rtemperaturesifrom 7-0 F: to 150 F; for: periods of up to "30 minutes, after which the'gurns' are removed by '--:oentr'ifugati'on. The resulting oil isv :called :a degummed oil but still oontaing coloured impurities and ireetfatty; acids. These latter are removedxin' asecond step involvingagitatin the oil with an aqueous- .solut'1on"of-an alkali -(oommonlymausticrsoda) under very. carefully controlledconditions;unti1 the-"soap which isiformedprecipitates'outvas a eoarse' curd whioh may be easily removdwby filtration-oncentrifugation. This :step requires v a skilled operator. in order to obtain au-sati-sfa'ctory "break :of the soap which ordinarilyrsis 'formed as: a finely divided suspensionwin theoil; i-he third stepconsists of mixing the degummed alkali refinedioilswith'a bleachin agent; rsuchr as: a suitable :clay' in an amount :up toaabout 53% of the:weight of theoil. The mixtureis :held' at elevated-temperatures, preferably inan inert atmosphere l oreven under a vacuum for hetween, fifteen: and thirty minutes;-,and then-is filtered. :The resulting'oil'isreferred to lasidegummed alkali- :refined; bleached oil. '-.Ihere-.-a-reappreciable losses: ot'oil-due to mechanical occlusion! atv eachstep and the overall loss by the time the-oil-emerges drom-thebleach fitfipumay bees high as eight to. ten-percent.

. .flfl'ieluseiof-l the term fmiscelladherein is intended-to define solution of a glyceride oil. in an extracting solvent.

Itis anobject of .the invention to. reduce overall-refining losses.

Another'object oi-the invention is to produce more-attractive-by=products such as every light coloured soap containing much-less neutraloil and light coloured-mots which are neutral.

A further object of the invention is to provide a process for refining vegetahle oilsin miscella wherein theoil-is subjected to a milder treatment throughout than formerly, thus resulting in a higher-tocopherol content"than that obtainable oyoon'venti nial-processes.

'A' still {further object of the invention is to provide -a-processfor "refining-vegetable "oi-ls in may be hexane and it is desired that the misc'el'la be received'from the extractorata temperature of about'150 'F. k v

"The first step of the processherein"embodies the decolourizin'g of thehot" misdellaby'me'ansibf a decolourizin-g agent suchas asuuaue "bleaching'clay by mixing it either continuously orbatchvvise therewi thin an amount upto' 3% byweight of'the oilin the miscella. lAny suitable 'bleaohing clay may-ice employed but a with a -bleahing clay known by'the trade mark' *Ion'sil the'olec'olourizing may continue for-about ninety seconds, after which the clay isremoved'by filtration and then the'decolour'i'zed miscella "may-be pum ed to ran-evaporator for partial removal of thesolvent-so'that theoil content-in the misclla reaches ahout'fifty'percent-bywei'ght. The usual bleaching clays 'm'ay requirea contact =period'of about SOminutes. I

The hot concentratclmiscella is then mixed either. 'continuou-sly or batchwise with-=an:=alkali refining agent such as- -sodiumlhydroxide or preferably acaustic brine of-sodium chloride-:solution containing an amount of sodium hydroxide calculated -to neutralize-thefree fatty acids. The reactioneis' very 'rapid and-the soaps-precipitate out in aboutone :minute, being removed centriiugallv.

Other salts such as sodium nitrate and sodium sulphate, may be employed for alkali refining where the --solutions of same contain 1 an amount of sodium hydroxide :for the pu-rpose of neutralizingtree fatty-acids.

The alkali refined 'misce'lla'ooncentrateis then subjected to' distillation *by which the-solvent is removed-to leave 'a'decolourized and alkali refined oil' whieh -still retains the 'ph'osphatides. The phosphatides may be-removed-in the'conventional manner T; by treating the solvent-free oil vswith water-landoentrifuging. :By varying 'ithe amount of water and timeof' agitationiall or part ofvrthe phosphatid'esmaybe' removed.

'L'The itiphosphatides r resultinguarea neutral and very rlightl'iin oolour andttheirtneutrality:considerably enhances their keeping qualities;

itlhfls :heenround that-itheiuseot caustimbrine in the alkali refining step has an advantage over the use of caustic soda alone in that the brine renders the soap insoluble in the aqueous phase. lhe presence of the brine also enables the separation of the soap to occur more rapidly and, moreover, inhibits emulsification in the alkali refining step.

A modification of the process herein involves combining two steps in one, that is, alkali refining and degumming. This is accomplished merely by increasing the contact time of the alkali refining step using caustic brine. Thus, for example, if a soybean miscella is treated with caustic brine for a period of ten minutes or more rather than for a relatively short period of, say, one minute, degumming takes place along with alkali refining to produce what is called in the trade a "breakfree oil."

In order to illustrate the process herein the following examples are presented.

Example 1 10 litres of soybean miscella of specific gravity 0.717 (obtained from the factory extractor) were warmed to 140 F. and agitated for 90 seconds with 40 grams of Tonsil AC (bleaching clay) and filtered. The filtrate was perfectly clear, golden yellow since much of the reddish colour had been removed. A sample of this filtrate when evaporated until free of solvent gave an oil of colour (Gardner-Holt scale).

litres of such decolourized soybean miscella was evaporated until the specific gravity (68 F.) rose to 0.790 (oil content about 52% by weight). The concentrated miscella was rapidly stirred while still hot, with 300 ml. of a solution containing 3% sodium hydroxide and 8% sodium chloride for 2 minutes, then centrifuged. A three phase system resulted consisting of miscella on top, a middle layer of solid soap and a lower aqueous brine layer containing some colouring matter derived from the oil. The soap layer was nearly white and could be used as an excellent starting source of fatty acids by those industries so engaged. Upon evaporation of the hexane from the refined miscella, a clear golden yellow soybean oil having a free fatty acid content of 0.04% by weight resulted.

Example 2 1000 grams of oil resulting from Example 1 were stirred at 140 F. with 25 ml. water for 30 minutes then centrifuged. A clear break-free soybean oil resulted and the foots had a very light cream colour. A titration of the foots indicated that the free fatty acid content was also 0.04% and they were remarkably stable against deterioration when stored at room temperature.

Example 3 A concentrated miscella prepared according to the bleaching and concentrating steps of Example 1 to an oil content of 55% and in the amount of 1 litre was stirred rapidly with 50 ml. of a solution containing 3% sodium hydroxide and 5% sodium chloride for ten to fifteen minutes to illustrate a modified process herein having combined refining and degumming steps. Upon removal of the solvent from the miscella the resulting oil had a free fatty acid content of 0.02% and was found to be substantially degummed.

A sample of 20 litres soybean miscella treated in accordance with the process steps outlined in Examples 1 and 2 showed an overall refining loss of oil of 5.0%.

It will be observed that the present process differs from prior processes of the same general character in that the steps are carried out in the presence of the extracting solvent and in substantially reverse order, resulting in lesser refining loss and more valuable by-products. Because of the presence of the solvent, less oil is in contact with the refining agent at any given moment, resulting in a greater yield of refined oil by reason of a reduction in refining losses. In addition, since comparatively low temperatures are employed throughout the process there is less chance for destruction of some of the labile anti-oxidants naturally present in the oil and hence the resulting refined oil has less tendency toward oxidative rancidity. Also by means of the present process the conditions may be adjusted so as to leave a trace of the phosphatides in the oil since the degumming step is performed after alkali refining. As a result a desired portion of the phosphatides may be retained to enhance the stability of the refined oil.

It is intended that the present disclosure should not be construed in any limiting sense apart from that indicated by the scope of the following claims.

What I claim as my invention is:

1. In a process for refining vegetable oils in hexane. the method of providing a refined vegetable oil containing bleached neutral phosphatides, comprising: decolourizing the vegetable oil while in hexane, then mixing the decolourized oil while in hexane, with an alkali refining agent containing only sufiicient sodium hydroxide to neutralize the free fatty acids thereof but providing retention of the phosphatides in the oil; and separating out the neutralized free fatty acids into soaps with a brine while neutralizing said free fatty acids.

2. The method as claimed in claim 1, and the step of: extracting the bleached neutral phosphatides from the refined oil after removal of the hexane therefrom by distillation.

3. The method as claimed in claim 1 and the step of: extracting only a portion of the bleached neutral phosphatides remaining in the refined oil to permit the latter to retain a suificient amount to act as a stabilizer.

4. The method of refining vegetable oils to obtain a refined vegetable oil containing bleached neutral phosphatides, comprising: forming a miscel a of the vegetable oil in hexane; decolourizing the miscella with a decolouring agent; removing the said decolourizing agent; mixing the decolourized miscella with an alkali refining agent containing only suflicient sodium hydroxide to neutralize the free fatty acids thereof but providing retention of the phosphatides in the oil; extracting soap stock from the neutralized decolourized miscella; and thereafter removing the hexane from said miscella to provide said refined oil.

5. The method according to claim 4, and the step of: removing the bleached neutral phosphatides from the oil after the hexane has been removed therefrom.

JOHN A. ZIEGLER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,260,731 Thurman Oct. 28, 1941 2,288,441 Ewing June 30, 1942 2,392,390 Julian Jan. 8, 1946 

1. IN A PROCESS FOR REFINING VEGETABLE OIL IN HEXANE, THE METHOD OF PROVIDING A REFINED VEGETABLE OIL CONTAINING BLEACHED NEUTRAL PHOSPHATIDES, COMPRISING: DECOLOURIZING THE VEGETABLE OIL WHILE IN HEXANE, THEN MIXING THE DECOLOURIZED OIL WHILE IN HEXANE, WITH AN ALKALI REFINING AGENT CONTAINING ONLY SUFFICIENT SODIUM HYDOXIDE TO NEUTRALIZE THE FREE FATTY ACIDS THEREOF BUT PROVIDING RETENTION OF THE PHOSPHATIDES IN THE OIL; AND SEPARATING OUT THE NEUTRALIZED FREE FATTY ACIDS INTO SOAPS WITH A BRINE WHILE NEUTRALIZING SAID FREE FATTY ACIDS. 